1. Field of the Invention
The present invention relates to a printing apparatus and a method for adjusting a printing position, and more particularly to a technique of adjusting the printing position of dots printed by scanning with a print head.
2. Description of the Related Art
In a printing apparatus, for example, in a case where printing is performed by bidirectional scanning in which a print head reciprocates in two directions, dots printed by forward and backward scan may be shifted from each other. To correct such a printing position error in the printing position of dots, it is known to perform processing for adjusting printing position in the scanning with the print head (hereinafter also referred to as “registration processing”). The registration processing is also performed, for example, to correct a printing position error in printing dots with print heads that perform printing by use of different colors.
In the process of obtaining an adjustment value used for adjusting a printing position in the registration processing, a plurality of patterns (hereinafter also referred to as “adjustment patterns”) are printed at different print timings. For example, in the case of bidirectional printing, with respect to a pattern printed by a forward scan, which serves as a reference pattern, a pattern is printed by a backward scan at a print timing shifted by a predetermined amount. A plurality of such a forward-backward pattern is printed with timings variously shifted by the predetermined amount. From the plurality of patterns, a pattern showing the smallest printing position error in the forward and backward scan printing is selected, and its predetermined shift amount is set as an adjustment value.
Some printing apparatuses can perform printing in a plurality of print modes that differ in a scanning speed, such as a print mode in which scanning is performed at a relatively high speed for a high print speed, a print mode in which scanning is performed at a relatively low speed for a high image quality, and the like. In a case where such printing apparatuses perform the registration processing, it is preferable to obtain an adjustment value for each scanning speed. Japanese Patent Laid-Open No. H11-291470(1999) discloses printing an adjustment pattern for each scanning speed and obtaining an adjustment value for each scanning speed based on a result obtained by reading the adjustment pattern. This allows appropriate registration processing according to the scanning speed in a case where the scanning speed varies depending on the print mode or the like.
However, a variation or a change in an ejection speed of the print head or a distance between the print head and a print medium may have an influence on the registration, and the influence level depends on the scanning speed. More specifically, the greater the scanning speed, the greater the adjustment value required to adjust a printing position which changes according to the variation or the like. In this case, the registration technique disclosed in Japanese Patent Laid-Open No. H11-291470(1999) may cause a problem that an appropriate adjustment value for eliminating a printing position error in the printing position goes beyond the range of the shift amount corresponding to the printed adjustment pattern. As a result, depending on the scanning speed, the obtained adjustment value may not be appropriate and the printing position may not be adjusted properly. To solve this problem, one may think of obtaining an appropriate adjustment value by extending the range of a shift amount as the scanning speed increases. In this case, it is required to print more adjustment patterns according to the extended range of the shift amount, and accordingly the load of the processing increases.